774 articles
Gill
Gill: the respiratory organ of fish and many aquatic animals, also the main site of osmoregulation, acid-base regulation, and ammonia excretion; countercurrent water flow over filaments and lamellae distinguishes it from lungs.
Gilt-head bream
Gilt-head bream (Sparus aurata; dorade royale, dorada), a Mediterranean and eastern Atlantic sparid fish and protandrous hermaphrodite, is the leading farmed finfish of Mediterranean aquaculture, with Greece and Turkey producing 72% of world output.
GloFish
GloFish is a trademarked brand of genetically modified freshwater aquarium fish that carry jellyfish and coral fluorescent genes and glow under blue light, first sold in 2003.
Glyptocephalus cynoglossus
Glyptocephalus cynoglossus, witch flounder or grey sole, is a deep-water right-eyed flatfish of the North Atlantic (Labrador to North Carolina and Europe), slow-growing and long-lived, IUCN Vulnerable, with several stocks under moratorium or rebuilding.
Gnathodus
Gnathodus (Pander, 1856) is an extinct conodont genus of the family Idiognathodontidae, an index fossil for Mississippian (Early Carboniferous) strata; nearly half of Mississippian conodont zones are defined by its species' first appearances, and it went extinct near the mid-Carboniferous boundary.
Gobiidae
Gobiidae (gobies) is the most species-rich fish family, about 2,000 species in roughly 250 genera of the order Gobiiformes, found in marine, brackish, and fresh waters, with fused pelvic fins, tiny body sizes, shrimp symbioses, and heavy aquarium-trade use.
Gobiiformes
Gobiiformes (gobies, gobioids) is an order of small, mostly benthic ray-finned fishes with 2,740 living species in 12 families, including Gobiidae, the most species-rich fish family, plus cardinalfishes, sleepers, and mudskippers.
Goblin shark
Goblin shark (Mitsukurina owstoni), sole living species of Mitsukurinidae; deep-sea lamniform shark to 3.9 m with slingshot jaws, ampullae-covered snout, first filmed alive in 2019/2024 Pacific sightings.
Goldfish
Goldfish (Carassius auratus), domesticated in ancient China from crucian carp, are a popular ornamental fish with over 300 varieties, long memory and spatial cognition, and invasive populations worldwide.
Gondolella
Gondolella (Stauffer & Plummer, 1932) is an extinct gondolellid conodont genus, type species G. elegantula, from Pennsylvanian Texas; gondola-shaped Pa elements used in Carboniferous-Permian biostratigraphy.
Gonostomatidae
Gonostomatidae (bristlemouths, portholefishes) is a family of small bioluminescent mesopelagic marine fishes in Stomiiformes; Cyclothone is among the most abundant vertebrate genera, and recent phylogenies revise its family limits.
Gourami
Gourami, or gouramies (Osphronemidae), freshwater labyrinth fishes of Asia and Africa with an air-breathing labyrinth organ; includes dwarf, pearl, honey, blue, and giant gouramis, bubble nesters and mouthbrooders popular in the aquarium trade.
Grass carp
Grass carp (Ctenopharyngodon idella), or white amur, is a large herbivorous Asian minnow introduced worldwide for aquatic weed control. Imported to the U.S. in 1963, it is established in the Mississippi basin and now regulated as invasive carp; triploid sterile fish are stocked for vegetation management.
Great hammerhead
The great hammerhead (Sphyrna mokarran) is the largest hammerhead shark, a tropical coastal predator whose large individuals prey mainly on other sharks and rays; it is Critically Endangered.
Great white shark
The great white shark, also called the white shark or white pointer (Carcharodon carcharias), is a large apex predatory shark found in temperate and subtropical seas worldwide.
Greenland shark
Greenland shark (Somniosus microcephalus), a North Atlantic and Arctic sleeper shark; longest-lived vertebrate, eye-lens radiocarbon dating giving 392 ± 120 years for the oldest specimen, maturity at ~156 years, fermented in Iceland as hákarl.
Grouper
Grouper is the common name for large, bottom-dwelling predatory reef fish of the subfamily Epinephelinae, with about 159 species; some are farmed, and the Nassau grouper is Endangered.
Guppy
Guppy (Poecilia reticulata), also millions fish, a small live-bearing poeciliid fish native to the Lesser Antilles and northern South America; popular aquarium fish, mosquito-control agent since World War I, High-risk invasive species, and model organism in evolutionary biology.
Gymnocephalus cernua
Gymnocephalus cernua, the ruffe or Eurasian ruffe (pope, blacktail), a small nocturnal percid fish native to Eurasia, introduced to Lake Superior by ballast water in the 1980s and an invasive competitor of yellow perch.
Gymnotiformes
Gymnotiformes, commonly known as the electric eels and knifefishes, is an order of strictly freshwater Neotropical fishes that generate electric discharges and sense the world through them.
Haddock
Haddock (Melanogrammus aeglefinus), scrod, a North Atlantic cod-family groundfish with a black thumbprint mark; lean sweet white flesh, major fish-and-chips species, U.S. stocks not overfished per 2024 assessments.
Haemulidae
Haemulidae (grunts), family Gill 1885 of tropical percomorph fishes, synonym Pomadasyidae; about 19 genera and 137 species in Atlantic, Indian, and Pacific oceans, named for pharyngeal-jaw stridulatory grunts.
Hagfish
Hagfishes, also known as slime eels, are eel-like deep-sea jawless vertebrates that scavenge on dead fish and repel predators with slime that clogs their gills.
Hákarl
Hákarl (kæstur hákarl) is Iceland's traditional fermented and dried Greenland shark (Somniosus microcephalus), documented since 1374; fermentation detoxifies toxic urea and TMAO, raising pH from 6 to 9, and the ammonia-scented result is eaten at þorrablót with Brennivín.
Hake
Hake is the common name for marine fish of the family Merlucciidae and related Phycidae, cod-like predators found near the sea floor at depths of over 1,000 meters that support major commercial fisheries on every continent.
Halibut
Halibut: large right-eyed flatfishes, chiefly Atlantic halibut (Hippoglossus hippoglossus) and Pacific halibut (Hippoglossus stenolepis), the world's largest flatfish; Atlantic stock overfished with 2055 rebuilding target, Pacific managed by the IPHC since 1923.
Hallucinogenic fish
Hallucinogenic fish, or ichthyoallyeinotoxism, is rare fish poisoning from species like Sarpa salpa (dreamfish, salema porgy), Siganus spinus, and Kyphosus, causing vivid hallucinations, nightmares, and delirium within minutes to 2 hours, lasting up to 24 hours.
Hammerhead shark
Hammerhead sharks (family Sphyrnidae, genera Sphyrna and Eusphyra) are sharks with a hammer-shaped cephalofoil bearing eyes and electroreceptors; eight to nine species, including scalloped, great, smooth, and bonnethead; threatened by fin fisheries, CITES Appendix II since 2013.
Harpadon nehereus
Harpadon nehereus, the Bombay duck (Loitta fish), is a lizardfish (Synodontidae) of Indo-West Pacific nearshore waters, a major dried and fresh food fish in India and Bangladesh, IUCN Near Threatened.
Harpoon
A harpoon is a spear-like hunting device whose detachable barbed head stays fastened by a line, used from early Holocene times to hunt large fish and marine mammals.